The purpose of this project is to develop methods for gene mapping in eukaryotic cells. Gene transfer is detected by isolation of colonies of biologically transformed cells in selective medium after incubation of isolated metaphase chromosomes with mutant recipient cells deficient in HPRT or TK. The gene product is further characterized as chromosomal donor species. The method currently may be most useful for determining close gene linkages. Nucleic acid hybridization is employed to determine the size of the transferred chromosome fragment (transgenome). Current estimates indicate that about 0.05 to 0.1 percent of the donor genome is present in a transcriptionally active form in transgenotes. BIBLIOGRAPHIC REFERENCES: McBride, O.W., and Athwal, R.S.: Genetic analysis by chromosome-mediated gene transfer. In Vitro 12: 777-786, 1976. McBride, O.W., and Athwal, R.S.: Chromosome-mediated gene transfer with resultant expression and integration of the transferred genes in eukaryotic cells. In Genetic Interaction and Gene Transfer. Brookhaven Symp. Biol. 29, 1977.